1. Field
Example embodiments relate to a magnetoresistive element, and more particularly, to a magnetoresistive element including a synthetic anti-ferromagnetic (SAF) structure.
2. Description of the Related Art
Due to developments in the information industry and requirements for processing mass information, there is an increasing demand for high capacity data storage media. Accordingly, research on compact data storage media with relatively fast data storage speeds has been conducted, and as a result, various kinds of data storage devices have been developed.
Data storage devices may be broadly classified into volatile data storage devices and non-volatile data storage devices. Volatile data storage devices have relatively fast writing and reading speeds, but information recorded on such devices is erased when the power is turned off. A representative example of a volatile data storage device is a dynamic random access memory (DRAM). On the other hand, information recorded on a non-volatile data storage device is not erased when power is turned off. Representative examples of non-volatile data storage devices include hard disk drives (HDD) and non-volatile random access memories (RAM).
A magnetoresistive random access memory (MRAM) is a type of non-volatile memory that uses a magnetoresistive effect based on spin transfer. A typical MRAM is formed of a magnetoresistive element and a switch, for example, a transistor. In general, the magnetoresistive element may include a giant magnetoresistive (GMR) structure and a magnetic tunnel junction structure. The magnetic tunnel junction is formed of a pinned layer, a tunneling barrier, and a free layer, which are sequentially stacked on an anti-ferromagnetic layer. Recent research into magnetic tunnel junctions has produced a tunnel junction that may include a synthetic anti-ferromagnetic (SAF) structure that reduces stray fields by forming a multi-layered pinned layer or a free layer.
FIG. 1 is a cross-sectional view of a magnetoresistive element including an SAF structure according to the conventional art. Referring to FIG. 1, an anti-ferromagnetic layer 12 is formed on a bottom layer 11, and a pinned layer having an SAF structure is formed on the anti-ferromagnetic layer 12. The pinned layer includes a first pinned layer 13, an intermediate layer 14 (e.g., an anti-ferromagnetic coupling spacer layer), and a second pinned layer 15 formed on the intermediate layer 14. A tunneling barrier 16, a free layer 17, and a top layer 18 are sequentially formed on the second pinned layer 15. The anti-ferromagnetic layer 12 is formed of an anti-ferromagnetic material including Mn, for example, PtMn. The first pinned layer 13, the second pinned layer 15, and the free layer 17 are formed of ferromagnetic materials. The intermediate layer 14 is formed of Ru, and the tunneling barrier 16 is formed of one selected from the group consisting of Mg oxide, Al oxide, Hf oxide and Ta oxide.
The magnetoresistive element, including the SAF structure as illustrated in FIG. 1, requires thermal treatment to crystallize materials that form the layers, for example, the Mg oxide forming the tunneling barrier 16. During the thermal treatment, material forming the intermediate layer 14 may diffuse into the first pinned layer 13 or the second pinned layer 15, such that material properties may deteriorate and/or thermal stability may be reduced.